This invention relates to a scanner, in particular to a paper feeding mechanism for the scanner.
Scanners are widely used today for reproducing an image digitally. In conventional technology, a contact image sensor and a roller of the scanner are installed on different structures. The main reason for using separate structures is that when the document is clamped, the paper clamped between the image contact sensor and the roller can be released.
A conventional contact image sensor, CIS contains a light source, a focusing lens and a sensor. It is an image reading head. Due to its small exterior dimensions and light weight, it is widely used in facsimile machines and paper-feeding image scanners. Today, small size and light weight are the direction where the industry devotes it development effort.
FIG. 1 shows the conventional design of a sheet feeding scanner. A contact sensor 1 has a glass window 1d. A document 3 to be scanned is pressure-fed by the roller 2 to engage the contact image sensor 1 and is scanned. The roller 2 is pressed against the document 1d by the radial arm 21 from an axis 9. The contact image sensor 1 has a spring 8a, which pushes the contact image sensor 1 against the roller 2 along the groove 7. Document 3 is fed through window 1d by the rotation of the roller and scanned by the contact image sensor 1.
Such products are sold commercially. For example, Microtek Inc. of Taiwan produces a sheet feeding scanner, under the trade name, Page Wiz; and an American company, Visioneer, produces a paper feeding scanner, under the trade name Paperport, etc. The length, width and height dimensions are 30 cmxc3x9710.5 cmxc3x975.5 cm and 30 cmxc3x976.3 cmxc3x979.0 cm, respectively. Since most paper feeding scanner are designed for use with standard A4 size papers, the width is usually 30 cm. Therefore, the size of the scanner is mostly determined by the cross-sectional dimension (perpendicular to the width) of the scanner, and the development effort of most companies is concentrated in reducing the cross-sectional dimensional area. For the afore-mentioned products, the cross-sectional areas are 10.5 cmxc3x975.5 cm and 6.3 cmxc3x979.0 cm, respectively. It is highly desirable to further reduce this cross-sectional area. In U.S. Pat. No. 5,621,544, Ogura et. al disclosed an image reading device, wherein a reading unit and a convey unit are integrally mounted on a U-shaped support unit. The reading unit and the convey unit can be disengaged by turning a semicircular cam against a spring which pushes the reading unit against the convey unit. Both the U-shaped support unit and the cam occupy more space in the housing and are undesirable.
An object of this invention is to unify the contact image sensor and the roller of a scanner in a single structure. Another object of this invention is to reduce the weight and volume of the structure. Still another object of this invention is to reduce the cost of the scanner.
These objects are achieved in this invention by unifying the contact image sensor and the roller of a scanner in one structure. The contact image sensor is pivoted on two sidewalls along an axis and is capable of turning with respect to that axis. This contact image sensor is pressed against a roller with a paper sandwiched between the contact image sensor and the roller. The pressure is exerted by the gravity of the contact image sensor which hangs above the roller and/or by a spring. The contact image sensor can be disengaged from the roller by pushing a release rod against the contact image sensor. The paper can be extracted when the release rod is actuated, or simply by pulling the paper harder. With this structure, the contact image sensor and the roller can be mounted on the same side walls, thus saving space.